A portable electronic device (PED) can be powered by an internal power supply (e.g., a chemical battery or otherwise) such that the PED can perform its capabilities for a useful life of the PED or power supply. A length of such useful life can be affected by a temperature of the power supply.
For example, a mobile wireless communications device—such as a cellular mobile telephone—is typically powered by a single battery (or battery pack) and capable of calling, e-mailing, texting, etc. Current drawn from the battery during operation of the device drops voltage of the battery and, in turn, drains its useful life, possibly even to a level causing the device to shut down. The voltage level and, thus, useful life of the battery is dependent upon its temperature [among other factors (such as age of the battery)]. More specifically, equivalent series resistance (ESR) of the battery varies inversely with the temperature. For example, as the battery temperature rises, the ESR falls, which increases the battery's voltage level and, thereby, useful life. In contrast, as the battery temperature falls, the ESR rises, which decreases the battery's voltage level and, thereby, useful life. In this way, performance of the battery and, hence, device are dependent upon the battery temperature.
Such a dependence becomes a concern especially when an environment in which the device is to be used is relatively cold (for instance, in geographical areas that experience relatively cold climates). The colder environment generally results in a shorter useful life of the device. This can be a concern in a situation in which it is impossible to place a call or send an e-mail or text message using the device before it shuts down.
Accordingly, there is a need to lengthen the useful life of a PED powered by an internal power supply. More specifically, there is a need to lengthen the useful life of a battery of a mobile wireless communications device, especially in lower- or reduced-temperature environments.